Dual fuel burner construction



Nov. 26, 1963 G. PEOPLES 3,111,979

DUAL FUEL BURNER CONSTRUCTION I Fileq March 7. 1960 I s Sheets-*Shet 1 V kjZVI/ENTOR.

ATTORNEYS.

Nov. 26, 1963 G. PEOPLES 3,111,979

DUAL FUEL BURNER CONSTRUCTION Filed March 7, 1960 I 3 Sheets-Sheet 2' 2a QJ 'Z ATTORNEYS.

Nov. 26, 1963 G. PEOPLES DUAL FUEL BURNER CONSTRUCTION 3 Sheets-Sheet 3 Filed March 7, 1960 //VVE/VTOR.' eapa/ ATTORNEm United States Patent of Iowa Filed Mar. 7, 1960, Ser. No. 13,245 3 Claims. (Cl. 1581l) This invention relates to a burner construction for churches, stores, factories and the like, designed particularly to burn either gas or oil, or a combination of the two.

One object of the invention is to provide a combination burner in which means for burning both gas and oil fuels are incorporated in a single unit for either constant or intermittent high heat output, and the cost of an extra burner is eliminated if a fuel changing type of operation is desired, or which, from the dealers standpoint, may be readily adapted for either straight gas or straight oil, whichever is available, or whichever is needed to suit specific requirements of certain customers.

Another object is to provide a combination burner in which gas and oil are introduced at two separate points in the same firing assembly so that neither burner has to compromise with the other in efficiency, the basic burner design being relatively simple and combustion of both fuels being very rapid and completed within a primary heat exchanger.

A further object is to provide a burner structure which introduces gas external to the oil to keep the oil nozzle cool during gas firing, the gas being introduced at right angles around the oil nozzle, the air vanes provided in the draft tube for oil burning continuing to supply combustion air for gas burning with highly turbulent and eflicient mixing of air and gas, the cool oil nozzle avoiding flash-back when switching from gas to oil, and my arrangement controlling the flame front positively and also providing fine control of the flame position as well as producing maximum flame stability and good combustion with a maximum of CO and minimum smoking.

Still a further object is to provide for interchangeable ignition means such as either gas pilot or direct spark ignition for oil burning, and gas pilot ignition for gas burning.

With these and other objects in view, my invention consists in the construction, arrangement and combination of the various parts of my furnace whereby the objects above contemplated are attained, as hereinafter more fully set forth, pointed out in my appended claims and illustrated in detail on the accompanying drawings, wherein:

FIG. 1 is a perspective view of a dual fuel furnace construction embodying my invention, parts thereof being broken away to show internal details;

FIG. 2 is a vertical sectional view through the burner of my furnace construction showing electric spark ignition for oil burning;

FIG. 3 is a perspective view of a combined gas pilot and electric spark ignition unit used when the burner is fired with gas, or with oil and gas;

FIG. 4 is a rear end elevation (right-hand end of FIG. 2) of the burner unit when adapted for burnin gas only; and

FIG. 5 is a front or discharge end elevation thereof.

On the accompanying drawings I have used the refer ence numeral to indicate in general a housing for my furnace construction. An acoustically lined front door 22 is provided at one end thereof spaced from which there is a double-walled partition 24-. The space between the door 22 and the partition 24 constitutes a burner vestibule in which all controls are hidden from sight, thus eliminating accidental bumping thereof and tampering therewith, as will hereinafter appear.

Inward of the partition 24 I provide a stainless steel tubular primary heat exchanger 26 having a front wall 28- ter- Sillfil Patented Nov. 25, 1963 'ice minating in a burner receiving tube fail. The rear end of the heat exchanger 26 is provided with an expansion joint comprising a front plate 34 and a rear plate 36 connected by thimbles 38 and 40 to a rear wall 32 of the heat exchanger and a rear flue box 42 respectively. The peripheries of the plates 34- and 36 are riveted or otherwise suitably secured together and the plates are spaced so that the spacing between them may decrease as the heat exchanger expands and increase as it contracts, thus producing a breathing action without straining the metal and thereby eliminating metal fatigue. This is a desirable feature under changing temperature conditions as it eliminates undesirable fracturing of joints or metal walls of the heat exchanger and associated parts.

The rear flue box 42 has a plurality of flues 44 communicating therewith and extending forwardly to communicate in turn with a front flue box 46. Each flue 44 has a corrugated baflle 45 therein and the flues constitute a secondary heat exchanger. The partition 24 constitutes a front wall for the flue box 46. To hold heat losses in the housing 20* to a minimum, a corrugated metal radiation shield we is provided, separated from the rear wall of the housing 20 by an air space 102.

The foregoing described heat exchanger and expansion joint are fully described and claimed in my copending divisional application Serial No. 118,073, filed June 19, 1961.

A combination induced draft and combustion air blower housing is provided which has a rear wall 52 and a front wall 54. A partition 58 divides the housing 51 into an induced draft blower section containing an induced draft blower wheel 61} and a combustion air blower section containing a combustion air blower wheel 62. The induced draft blower section has a discharge opening 64 communicating with a flue outlet section 66 of the housing 50. The flue section 66 has a top flue opening and a side flue opening. The side flue opening is covered by a flue opening cover plate 72, and a flue extension 74 is shown associated with the top flue opening.

Associated with the blower wheel 60 is a suitable blower scroll for directing the products of combustion from the blower wheel into the flue outlet section 66.

The combustion air blower wheel 62 receives air from the burner vestibule through an opening 86 in the front wall 54 0f the housing 50 and discharges it into the lower part of the housing as directed by a second suitable scroll to enter the burner unit as will hereinafter appear.

Both blower wheels 60 and 62 are mounted on the same blower shaft 90 supported by a bearing assembly 92 which in turn is supported on the front wall 54- by three supporting brackets 94. The shaft 90 is driven by a V-belt 96 from a motor 98 whereby both blower wheels 60 and 62 are driven by the same motor. By mounting both blower wheels 60 and 62 on a single shaft and driving them from a single motor, both manufacturing costs and maintenance are reduced to elfect extra economy, and fewer parts are involved to service. This arrangement also contributes to quietness of operation. By having the blower wheels on opposite sides of the partition 58 which is heated by the products of combustion (usually about 600 F.) flowing past it from the discharge opening 64 to the flue outlet section 66, all combustion air is preheated for maximum efiiciency of ope-ration of the burner. The bearing assembly 92 is isolated from the hot blower wheel 60 by the cooler blower wheel 62 and the partition 58, and since the bearing assembly is located in the inlet opening 86 where room air at about is flowing into the blower wheel 62, the bearing assembly runs relatively cool because of room air being constantly drawn thereover, yet both blowers can be regulated separately to obtain the most eflicient combustion and provide the correct draft for particular installations.

Both blower wheels are also simultaneously operable during pre-purge and post-purge periods to provide rapid purge of the combustion chamber by blowing room air into its intake end and withdrawing gases from its discharge end. It will be noted that the burner axis and the axes for the blowers and their motor are all parallel to each other so that the entire furnace construction can be installed upright as shown, on its side (horizontal) or inverted and suspended from the ceiling if desired to suit a variety of different installations and fit various available space shapes.

The foregoing described dual blower arrangement is fully described and claimed in my copending divisional application Serial No. 118,074, filed June 19, 196 1.

The furnace housing may be mounted on a blower housing shown generally at 104 having discharge openings 106 for air as indicated by arrows in FIG. 1 to circulate around the primary and secondary heat exchangers 26 and 44. This air then flows into the top of housing 20 which serves as a plenum chamber for heated air discharge outlets 108 provided with adjustable deflector blades 110 so that the heated air is properly directed throughout the area to be heated as desired for comfortable temperatures at working levels. Alternatively, duct distribution systems can be associated with the outlets 108.

The blower housing 104 has a pair of blowers 172 mounted therein. The blower wheels 173 of the blowers 172 are mounted on a single shaft 175 and driven by a belt 174 from a motor 176. Grills 178 permit entrance of air into the blower housing 104 to be forced by the blowers around the heat exchangers 26- and 44 and through the plenum chamber thereabove to the discharge outlets 108.

Describing next the burner unit shown particularly in FIG. 2 and indicated generally as B, an outer tube 112 surrounds a draft tube 114- and is spaced therefrom to provide, in conjunction with end discs 115 and 117, a gas chamber 116, and part of the outer tube 112 extends beyond the gas chamber to serve as a support for a cylindershaped refractory 118. It will be understood that any suitable material, such as stainless steel, may be used in place of a refractory to provide a gas chamber of the same predetermined diameter and length. The diameter and length of the gas chamber will be determined in accordance with the input range of the fuel, regardless of the type of fuel being used. The outer tube 112 is located in the burner receiving tube of the primary heat exchanger 26.

Outer and inner draft swirl sleeves 120 and 122 are provided for swirling the air that is discharged from the scroll into the lower portion of the housing 50, and which air enters the right-hand end of the draft tube 114 in FIG. 2. A nozzle and igniter assembly is shown comprising a fuel oil atomizing nozzle 124 mounted in a support 126 having a plurality of arms 1% fitting in the draft tube 114, a fuel oil pipe 130 extending from the support 1 26 and a. pair of high tension insulators 132 supporting spark electrodes 134 for the ignition of oil. It is contemplated that multiple fuel oil nozzles may be used Where it is desired to perform staged starting and multiple selection rates.

A second ignition shown in FIG. 3 is also provided wherein there is 'but a single electrode insulator 132 and a single electrode 134 combined with a gas pilot burner 136 mounted on a supporting bracket 146. A gas line 133 leads to the burner 136 and a pilot shield 144 is provided for the pilot flame and supported on a scanner tube 140. A supporting flange 142. serves to removably position the parts on the outer wall of the gas chamber 116 as shown in FIGS. 2 and 4, and is provided with upper, central and lower holes 141, 143 and 145 respectively for the insulator 132, gas line 133 and scanner tube 140. Electric spark ignition from the electrode 134 initially lights the pilot burner 136. in FiG. 2, the supporting flange 142 only is illustrated, the parts 4 132, 138 and 134 being omitted. The assembly just described is enclosed in a kidney-shaped tube 172 which extends throughout the length of the gas chamber 116, opening through the end discs and 117.

A gas supply pipe 148 leads to the chamber 116 and the draft tube 114 is provided with brass eyelets 150 serving as corrosition resistant gas discharge ets. These eyelets are readily replaceable with others of different size for varying the gas discharge capacity as desired.

The second ignition assembly, the gas supply pipe 148, the chamber 116 and the jets 150* provide for gas to be burned either alone or in conjunction with fuel 011.

I have found the number of jets critical. For example, eight jets of a predetermined diameter produce smooth burning action when burning natural gas at input rates in the range of 490,000 to 630,000 B.t.u.s, whereas twelve or sixteen jets cause a frequency to be set up resulting in undesirable flame resonance. However, liquified petroleum gases require the use of ten ets of a smaller predetermined diameter at the same input rates in order to provide resonant-free operation. Each different type of gaseous fuel and range of input rates requires a critical selection of the correct number and predetermined diameter of jets. I

With the installation shown in FIG. 2, e ther ml or gas may be burned, or both oil and gas may be burned. Usually, however, when gas is burned alone or 1n combination with fuel oil, the installation of P16. 3 with a gas pilot burner is preferable. With both gas and O1] fuels incorporated in a single burner unit, the cost of an extra burner when changing fuels is eliminated and the burner is available if desired for either straight gas or oil, instead of a combination of the two. Since the gas and oil are introduced at two separate points in the same firing assembly, one bumer does not have to compromise with the other in elficiency. Combustion of both fuels is very rapid and is substantially completed within the refractory 118, and fully completed within the stainless steel primary heat exchanger 26. It is unnecessary to change or reset combustion air or draft when direct spark ignited oil is used as the solenoid 158 for operating the damper 154 may be connected into the control c rcu t 1n such a way that it is energized during the tI'lal-fOf-lgl'llPlOl'l period, acting in effect as an air choke, and de-energized immediately following that period, thereupon automatically opening the damper 154 to the pre-set position during normal operation of the burner to provide optimum a r for efllcient oil combustion. When the damper 154 15 used for high-lowed or two-stage gas-fired operation, the solenoid 158 may be connected into the control circuit in such a way that it is energized to place the damper 154 in the minimum combustion air position for low fire or reduced gas input, and de-energized to place the damper in pre-set open position for high fire or maximum gas input. By introducing the gas from the arrangement of jets 150 on the discharge side of the oil nozzle 124, the oil nozzle is kept cool during gas firing and the introduction of gas at right angles to and around the oil nozzle enables the vanes of the swirl sleeves and 122 to continue to supply combustion air and keep the oil nozzle cool to avoid flashback when later switching from gas to oil. The arrangement also controls the flame front positively with fine control of the flame position (illustrated at 27 in FIG. 1) and increases flame stability with good combustion on both fuels without any change in combustion air setting, and the unit is not position sensitive. Most of the component parts of the gas and oil burner are the same, the basic gas burner design being extremely simple and very practical with the gas introduced at right angles to the flow of combustion air creating a highly turbulent and et'ficient mixing of air and gas and a maximum of rapidity in combustion. As far as the dealer is concerned, dual fuel burners are available and interchangeable with single fuel burners.

When fuel oil is being burned, a fuel il pump 1 9 (see FIG. 1) is provided and driven by a belt 162 from the blower shaft 91). When only gas is being burned the fuel oil pump can be omitted and thus the dealer has a means to readily convert the basic furnace construction to oil heat, gas heat, or a combination of the two before it is sent out for installation.

The burner vestibule may have the various furnace controls such as 164 and 166 mounted therein, as well as the solenoid 158 as shown in FIG. 1. An access and inspection door 168 for the burner is also located therein normally covering an opening 170 in the front wall 54 of the housing 50.

Some changes may be made in the construction and arrangement of the parts of my dual fuel furnace without departing from the real spirit and purpose of my invention, and it is my intention to cover by my claims any modified forms of structure or use of mechanical equivalents which may reasonably be included within their scope.

I claim as my invention:

1. In a dual fuel burner construction of the character disclosed, a draft tube, a first swirl sleeve telescopically mounted therein, coaxial therewith, and having radially inwardly projecting vane means, said vane means being spirally arranged to swirl the air passing therethrough in one direction of rotation, said draft tube extending forwardly beyond said sleeve and having gas discharge openings through the wall thereof which have axes at right angles to the axis of said draft tube, said gas discharge openings being located immediately in front of said swirl sleeve, means forming a gas chamber surrounding said draft tube, a gas supply pipe leading thereto, a second swirl sleeve telescopically mounted inside said first swirl sleeve and coaxial therewith, said second swirl sleeve having radially inwardly projecting vane means spirally arranged to swirl the air passing therethrough in the same direction as said one direction of rotation and having an open center for the oil flame, the downstream ends of said swirl sleeves being substantially coincident, and a fuel oil nozzle and spark electrode assembly in said draft tube and having the fuel oil nozzle and the spark electrodes thereof located within said second swirl sleeve, the discharge end of said oil nozzle terminating substantially coincident with the upstream end of said second swirl sleeve, said burner being adapted for burning both gas and fuel oil with combustion thereof completed beyond the discharge end of said draft tube.

2. In a dual fuel burner construction, a draft tube, swirl sleeve means and an oil burner assembly telescopically mounted therein coaxial therewith, said swirl sleeve means having radially inwardly projecting vane means, said vane means being spirally arranged to swirl the air passing therethrough in one direction of rotation, said draft tube extending forwardly beyond said swirl sleeve means and having gas discharge openings through the wall thereof, said gas discharge openings having axes at right angles to the axis of said draft tube for creating a highly turbulent and eflicient mixing of air and gas with maximum rapidity of combustion and to keep the oil nozzle cool during gas burning, said gas discharge openings being located immediately in front of said swirl sleeve means, said oil burner assembly including an oil nozzle located in said swirl sleeve means and separated by a portion thereof from said gas discharge openings, means forming a gas chamber surrounding the entire length of said draft tube and communicating with said gas discharge openings, and a gas supply pipe leading thereto, said burner being thereby adapted for burning both gas and fuel oil, or each separately.

3. A dual fuel burner construction comprising a draft tube, a pair of draft swirl sleeves telescopically mounted therein, one within the other, both coaxial with respect to said draft tube, having downstream ends substantially coincident with each other and both being provided with radially inwardly projecting vane means, said vane means being spirally arranged to swirl the air passing therethrough in one direction of rotation, means forming a gas chamber surrounding said draft tube and having gas discharge openings into said draft tube, the axes of said gas discharge openings being at right angles to the axis of said draft tube and said gas discharge openings being located immediately in front of said swirl sleeves, and a fuel oil nozzle and spark electrode assembly telescopically and removably mounted in said draft tube and having the fuel oil nozzle thereof located within the outer one of said draft swirl sleeves and terminating substantially coincident with the upstream end of the inner one thereof, the spar-k electrodes of said assembly being located within the inner one of said draft swirl sleeves, said burner being adapted for burning both gas and fuel oil with combustion completed beyond the discharge end of said draft tube.

References Cited in the file of this patent UNITED STATES PATENTS 750,590 Burpee Jan. 26, 1904 1,644,180 Croan Oct. 4, 1927 2,353,606 Watts July 11, 1944 2,458,542 Urquhart Jan. 11, 1949 2,632,501 Clark Mar. 24, 1953 2,635,813 Schlenz Apr. 21, 1953 2,753,929 Walshin July 10, 1956 2,821,246 Ide et a1. Jan. 28, 1958 2,822,864 Black Feb. 11, 1958 2,826,249 Poole Mar. 11, 1958 2,838,103 Voorheis June 10, 1958 

1. IN A DUAL FUEL BURNER CONSTRUCTION OF THE CHARACTER DISCLOSED, A DRAFT TUBE, A FIRST SWIRL SLEEVE TELESCOPICALLY MOUNTED THEREIN, COAXIAL THEREWITH, AND HAVING RADIALLY INWARDLY PROJECTING VANE MEANS, SAID VANE MEANS BEING SPIRALLY ARRANGED TO SWIRL THE AIR PASSING THERETHROUGH IN ONE DIRECTION OF ROTATION, SAID DRAFT TUBE EXTENDING FORWARDLY BEYOND SAID SLEEVE AND HAVING GAS DISCHARGE OPENINGS THROUGH THE WALL THEREOF WHICH HAVE AXES AT RIGHT ANGLES TO THE AXIS OF SAID DRAFT TUBE, SAID GAS DISCHARGE OPENINGS BEING LOCATED IMMEDIATELY IN FRONT OF SAID SWIRL SLEEVE, MEANS FORMING A GAS CHAMBER SURROUNDING SAID DRAFT TUBE, A GAS SUPPLY PIPE LEADING THERETO, A SECOND SWIRL SLEEVE TELESCOPICALLY MOUNTED INSIDE SAID FIRST SWIRL SLEEVE AND COAXIAL THEREWITH, SAID SECOND SWIRL SLEEVE 